The entire disclosures of Japanese Patent Application Nos. 2000-116337 filed on Apr. 18, 2000 and 2001-61327 filed on Mar. 6, 2001, including specifications, claims, drawings and summaries are incorporated herein by reference in their entirety.
1. Field of the Invention
The present invention relates to a steam control apparatus for a turbine which introduces steam from a waste heat recovery boiler, or fluid from an auxiliary passage, to a blade ring of a gas turbine and a high-temperature component, such as a combustor, to thereby effect temperature control.
2. Description of the Related Art
From the viewpoint of economy and effective use of energy resources, various measures for improving efficiency have been implemented in power generation facilities (power generation plants). One measure is employment of a turbine power generation plant (a combined cycle power generation plant) in which a gas turbine and a steam turbine are combined. In a combined cycle power generation plant, high-temperature exhaust gas from a gas turbine is fed to a waste heat recovery boiler, in which steam is generated via a superheating unit, and the thus-generated steam is fed to a steam turbine, in which the generated steam performs work.
High-temperature components, such as a combustor, of a gas turbine has been cooled by means of air. However, in order to cope with a recent increase in combustion temperature, cooling by means of steam has come into use. In relation to a combined cycle power generation plant as well, there is a plan to use a steam turbine in combination with a gas turbine in which high-temperature components such as a combustor are cooled by means of steam, to thereby obtain a highly efficient power generation plant. Moreover, in order to cope with a recent increase in operation temperature of a gas turbine, various studies have been performed on a technique for introducing steam to the blade ring portion of the turbine so as to optimally control the clearance between the blade ring portion and moving blades. That is, there is a plan to effect temperature control by means of steam in order to prevent contact between the moving blades and the blade ring portion at the time of startup and to maintain a minimum clearance between the moving blades and the blade ring portion during ordinary operation, to thereby achieve safety and high efficiency simultaneously.
In relation to a combined cycle power generation plant, various studies have been performed on a technique for introducing steam to the blade ring portion of the turbine so as to optimally control the clearance between the blade ring portion and moving blades and for cooling high-temperature components such as a combustor by means of steam.
Control of the clearance between the moving blades and the blade ring portion must be performed differently from cooling of high-temperature components such as a combustor by means of steam. Specifically, the clearance control must be performed such that at the time of startup, the clearance is made relatively large through introduction of steam of relatively high temperature, and during ordinary operation, the clearance is made relatively small through introduction of steam of relatively low temperature. In contrast, cooling of high-temperature components must be performed through introduction of steam of low temperature. As described above, when control of the clearance between the moving blades and the blade ring portion by means of steam and cooling of high-temperature components, such as a combustor, by means of steam are performed, steam must be introduced while the flow rate of steam, etc. are controlled in order to simultaneously satisfy a temperature requirement in clearance control and a temperature requirement in cooling. However, in the existing combined cycle power generation plant, a satisfactory technique for steam control which satisfies the two different requirements regarding temperature has not been established.
In view of the foregoing, an object of the present invention is to provide a steam control apparatus for a turbine which can achieve control of the clearance of a blade ring portion by means of steam and cooling of high-temperature components such as a combustor by means of steam.
In order to achieve the above object, the present invention provides a steam control apparatus for a turbine, comprising a waste heat recovery boiler including a high-pressure unit for generating high-pressure steam by use of exhaust gas of the gas turbine, and a low-pressure unit for generating low-pressure steam by use of exhaust gas of the gas turbine. A steam turbine is operated by means of steam generated by the waste heat recovery boiler. A low-pressure-side steam introduction passage introduces low-pressure steam from the low-pressure unit of the waste heat recovery boiler to the steam turbine. A high-pressure-side steam introduction passage introduces high-pressure steam from the high-pressure unit of the waste heat recovery boiler to the steam turbine. A steam passage branches off the low-pressure-side steam introduction passage and serves as a bypass for introducing low-pressure steam from the low-pressure unit to a blade ring of the gas turbine and a high-temperature component. A high-pressure steam passage branches off the high-pressure-side steam introduction passage and merges into the steam passage on the upstream side of the blade ring of the gas turbine and the high-temperature component. A flow-rate adjustment-control unit adjusts the flow rate of steam flowing through the steam passage and the flow rate of steam flowing through the high-pressure steam passage to thereby adjust the flow rate and temperature of steam flowing through the blade ring of the gas turbine and the high-temperature component. In the steam control apparatus of the present invention, since the temperature and flow rate of steam introduced to the turbine and the high-temperature component can be controlled properly through mixing high-pressure steam and intermediate-pressure steam, two different requirements, i.e. adjustment of steam temperature and securing of a sufficient steam flow rate, can be satisfied simultaneously. As a result, it becomes possible to simultaneously achieve control of the clearance of the blade ring by means of steam and cooling of the high-temperature component by means of steam.
Preferably, the flow-rate adjustment-control unit comprises a first flow control valve provided in the low-pressure-side steam introduction passage on the downstream side of the branching portion of the steam passage and adapted to control the flow rate of steam flowing through the steam passage through adjustment of the flow rate of steam flowing through the steam turbine. A second flow control valve is provided in the high-pressure steam passage and adapted to control the temperature of steam flowing through the steam passage through adjustment of the flow rate of high-pressure steam. A temperature detector detects the temperature of steam flowing thorough the steam passage on the downstream side of the merging portion of the high-pressure steam passage. A pressure detector detects the pressure of steam flowing through the steam passage on the downstream side of the merging portion of the high-pressure steam passage. A control unit controls the first and second flow control valves on the basis of the temperature detected by the temperature detector and the pressure detected by the pressure detector in order to maintain, at predetermined values, the flow rate and temperature of steam flowing through the blade ring of the gas turbine and the high-temperature component.
In this case, two different requirements, i.e., adjustment of steam temperature and securing of a sufficient steam flow rate, can be satisfied simultaneously without use of expensive detection means or valve members.
Preferably, the high-temperature component is a combustor. The pressure detector is a differential-pressure detector for detecting a difference in steam pressure between the inlet and outlet of the combustor. An auxiliary fluid introduction passage having a third flow control valve merges into the high-pressure steam passage on the downstream side of the second flow control valve. A second temperature detector is provided in the high-pressure steam passage on the downstream side of the merging portion of the auxiliary fluid introduction passage. The control unit has a function for opening and closing the first flow control valve on the basis of detection information output from the differential-pressure detector, opening and closing the second flow control valve on the basis of detection information output from the differential-pressure detector and detection information output from the temperature detector, and opening and closing the third flow control valve on the basis of detection information output from the second temperature detector, such that the flow rate of steam flowing through the steam passage increases with output of the gas turbine, and the steam temperature decreases to a predetermined temperature.
In this case, the two different requirements, i.e., adjustment of steam temperature and securing of a sufficient steam flow rate, can be satisfied simultaneously and optimally, in accordance with the operation conditions of the gas turbine.
Preferably, the control unit has a function used when the second flow control valve is opened and closed on the basis of detection information output from the differential-pressure detector and detection information output from the temperature detector. The function is adapted to compare an open/close command determined on the basis of the detection information output from the differential-pressure detector and an open/close command determined on the basis of the detection information output from the temperature detector and open and close the second flow control valve on the basis of the open/close command which designates a larger opening.
In this case, high-pressure steam can be used as backup steam in order to secure a desired flow rate.
Preferably, the control unit has a function for judging whether the second flow control valve is opened and closed on the basis of the open/close command derived from the detection information output from the differential-pressure detector or the open/close command derived from the detection information output from the temperature detector and a function for setting the opening of the third flow control valve for the case in which the open/close command determined on the basis of the detection information from the differential-pressure detector is used, such that the opening becomes greater than that of the third flow control valve for the case in which the open/close command determined on the basis of the detection information from the temperature detector is used.
In this case, the temperature of high-pressure steam is changed in accordance with the type of control applied to high-pressure steam, whereby the flow rate of the high-pressure steam can be minimized.
Preferably, the high-temperature component is. a combustor. The pressure detector is a differential-pressure detector for detecting a difference in steam pressure between the inlet and outlet of the combustor. An auxiliary fluid introduction passage having a third flow control valve merges into the high-pressure steam passage on the downstream side of the second flow control valve. A second temperature detector is provided in the high-pressure steam passage on the downstream side of the merging portion of the auxiliary fluid introduction passage. The control unit has a function for opening and closing the first flow control valve on the basis of detection information output from the temperature detector, opening and closing the second flow control valve on the basis of detection information output from the differential-pressure detector, and opening and closing the third flow control valve on the basis of detection information output from the second temperature detector, such that the flow rate of steam flowing through the steam passage increases with output of the gas turbine, and the steam temperature is lowered to a predetermined temperature.
In this case, the temperature and flow rate of steam introduced to the blade ring of the turbine and the high-temperature component can be controlled properly through mixing intermediate-pressure steam and high-pressure steam, and two different requirements, i.e. adjustment of steam temperature and securing of a sufficient steam flow rate, can be satisfied simultaneously.
The present invention further provides a steam control apparatus for a turbine, comprising a waste heat recovery boiler including a high-pressure unit for generating high-pressure steam by use of exhaust gas of the gas turbine and a low-pressure unit for generating low-pressure steam by use of exhaust gas of the gas turbine. A steam turbine is operated by means of steam generated by the waste heat recovery boiler. A low-pressure-side steam introduction passage introduces low-pressure steam from the low-pressure unit to the steam turbine. A high-pressure-side steam introduction passage introduces high-pressure steam from the high-pressure unit to the steam turbine. A steam passage branches off the low-pressure-side steam introduction passage and serves as a bypass for introducing low-pressure steam from the low-pressure unit to a blade ring of the gas turbine and a high-temperature component. Aa first flow control valve is provided in the low-pressure-side steam introduction passage on the downstream side of the branching portion of the steam passage and adapted to control the flow rate of steam introduced to the steam passage. A passed-steam-temperature detector detects the temperature of steam after passing through the blade ring of the gas turbine and the high-temperature component. A control unit opens and closes the first flow control valve on the basis of detection information output from the passed-steam-temperature detector in order to adjust the flow rate of steam introduced to the steam passage to thereby maintain, at a predetermined level, the flow rate of steam flowing through the blade ring of the gas turbine and the high-temperature component.
In this steam control apparatus, since the temperature and flow rate of steam introduced to the turbine and the high-temperature component can be controlled properly through mixing intermediate-pressure steam and high-pressure steam, two different requirements, i.e. adjustment of steam temperature and securing of a sufficient steam flow rate, can be satisfied simultaneously. In addition, when the steam temperature increases as a result of performance of temperature control, the first flow control valve is controlled to increase the flow rate of steam introduced to the blade ring of the gas turbine and the high-temperature component so that the flow rate of steam for temperature control increases, and the blade ring and the high-temperature component are protected. As a result, it becomes possible to simultaneously achieve control of the clearance of the blade ring by means of steam and cooling of the high-temperature component, such as a combustor, by means of steam, with high reliability. In addition, the blade ring and the high-temperature component can be protected without use of an interlock function, even when the outlet side temperature of the high-temperature component increases.
The present invention further provides a steam control apparatus for a turbine, comprising a waste heat recovery boiler including a high-pressure unit for generating high-pressure steam by use of exhaust gas of the gas turbine and a low-pressure unit for generating low-pressure steam by use of exhaust gas of the gas turbine. A steam turbine is operated by means of steam generated by the waste heat recovery boiler. A low-pressure-side steam introduction passage introduces low-pressure steam from the low-pressure unit to the steam turbine. A high-pressure-side steam introduction passage introduces high-pressure steam from the high-pressure unit to the steam turbine. A high-pressure steam passage branches off the high-pressure-side steam introduction passage and serves as a bypass for introducing high-pressure steam to a blade ring of the gas turbine and a high-temperature component. A second flow control valve is provided in the high-pressure steam passage. A passed-steam-temperature detector detects the temperature of steam after passing through the blade ring of the gas turbine and the high-temperature component. A control unit opens and closes the second flow control valve on the basis of detection information output from the passed-steam-temperature detector in order to adjust the flow rate of steam flowing trough the high-pressure steam passage to thereby maintain at a predetermined level, the flow rate of steam flowing through the blade ring of the gas turbine and the high-temperature component.
In the steam control apparatus of the present invention, since the temperature and flow rate of steam introduced to the blade ring of the turbine and the high-temperature component can be controlled properly through mixing intermediate-pressure steam and high-pressure steam, two different requirements, i.e. adjustment of steam temperature and securing of a sufficient steam flow rate, can be satisfied simultaneously. In addition, when the steam temperature increases as a result of performance of temperature control, the second flow control valve is controlled to increase the flow rate of steam introduced to the blade ring of the gas turbine and the high-temperature component, so that the flow rate of steam for temperature control increases, and the blade ring and the high-temperature component are protected. As a result, it becomes possible to simultaneously achieve control of the clearance of the blade ring by means of steam and cooling of the high-temperature component, such as a combustor, by means of steam, with high reliability. In addition, the blade ring and the high-temperature component can be protected without use of an interlock function even when the outlet side temperature of the high-temperature component increases.
The present invention further provides a steam control apparatus for a turbine, comprising a waste heat recovery boiler including a high-pressure unit for generating high-pressure steam by use of exhaust gas of the gas turbine and a low-pressure unit for generating low-pressure steam by use of exhaust gas of the gas turbine. A steam turbine is operated by means of steam generated by the waste heat recovery boiler. A low-pressure-side steam introduction passage introduces low-pressure steam from the low-pressure unit to the steam turbine. A high-pressure-side steam introduction passage introduces high-pressure steam from the high-pressure unit to the steam turbine. A steam passage branches off the low-pressure-side steam introduction passage and serves as a bypass for introducing low-pressure steam from the low-pressure unit to a blade ring of the gas turbine and a high-temperature component. A high-pressure steam passage branches off the high-pressure-side steam introduction passage and merges into the steam passage on the upstream side of the blade ring of the gas turbine and the high-temperature component. A first flow control valve is provided in the low-pressure-side steam introduction passage on the downstream side of the branching portion of the steam passage and adapted to control the flow rate of steam introduced to the steam passage. A second flow control valve is provided in the high-pressure steam passage. A passed-steam-temperature detector detects the temperature of steam after passing through the blade ring of the gas turbine and the high-temperature component. A control unit opens and closes the first flow control valve on the basis of detection information output from the passed-steam-temperature detector in order to adjust the flow rate of steam introduced to the steam passage, and opens and closes the second flow control valve on the basis of detection information output from the passed-steam-temperature detector in order to adjust the flow rate of steam flowing trough the high-pressure steam passage, to thereby maintain, at a predetermined level, the flow rate of steam flowing through the blade ring of the gas turbine and the high-temperature component.
In this steam control apparatus, the flow rate and temperature of steam introduced to the blade ring of the gas turbine and the high-temperature component can be controlled properly, so that two different requirements, i.e. adjustment of steam temperature and securing of a sufficient steam flow rate, can be satisfied simultaneously. In addition, when the steam temperature increases as a result of performance of temperature control, the first and second flow control valves are controlled to increase the flow rate of steam introduced to the blade ring of the gas turbine and the high-temperature component so that the flow rate of steam for temperature control increases and the blade ring and the high-temperature component are protected. As a result, it becomes possible to simultaneously achieve control of the clearance of the blade ring by means of steam and cooling of the high-temperature component, such as a combustor, by means of steam with high reliability. In addition, the blade ring and the high-temperature component can be protected without use of an interlock function even when the outlet side temperature of the high-temperature component increases.
Preferably, a fourth flow control valve is provided in the steam passage on the downstream side of the blade ring of the gas turbine and the high-temperature component and the control unit has a function for opening and closing the fourth flow control valve on the basis of detection information output from the passed-steam-temperature detector in order to control the flow rate of steam flowing through the steam passage to thereby secure the steam flow rate of the steam passage and a function for fully opening the fourth flow control valve when the passed-steam-temperature detector detects that the steam temperature exceeds an upper limit.
In this case, when the steam temperature exceeds the upper limit, steam can flow through the steam passage at the maximum flow rate.